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  • Sample of a mezzanine column investigation


    Investigation of Existing Columns for New Mezzanine Loads

    TABLE OF CONTENTS


    I. Introduction

    II. Background

    III. Mezzanine Information

    IV. Existing Column Checks & Results

    V. Proposed Column Modifications & Solutions

    VI. Conclusions and notes

    VII. Appendix

    I. Introduction

    A preliminary engineering investigation has been undertaken to address the
    proposed building changes only as they affect existing
    building columns due to the addition of a 50' x 165' x 12' high mezzanine to an existing
    metal building.

    The objective of this engineering investigation was basically twofold in nature:

    1) to determine the extent of the structural impact and effects on certain metal building
    rigid frame sidewall built-up columns, interior pipe columns, along with specific
    endwall columns along line 1.

    2) to suggest structural modifications, changes, alterations or similar improvements to
    the existing columns so that it can properly support the added mezzanine loads and
    forces.

    II. Background

    The building in question is a pre-engineered metal building manufactured by an MBMA certified producer. It is
    a gabled structure measuring 200' wide by 250' long having a low eave height of 25' and a
    roof slope of 1/4:12.

    The primary frames are modular, gabled rigid frames with spans of 4 @ 50' and are spaced
    at 50' on center with intermediate sidewall wind columns @ 25' spacings. The interior
    frame columns are 10'' diameter pinned top and bottom pipe columns. Endwall line 1 is a
    post & beam type consisting of 12'' deep built-up and wideflange column members.


    III. Mezzanine Information

    Mezzanine size: 60' wide X 165' long X 12' high.
    Mezzanine Loads: Total Dead Load = 50 psf
    Total Live Load = 50 psf
    Total Load = 100 psf

    See attached sketches showing the proposed layout of support steel which denote 6
    different existing column types affected by the new mezzanine loads.

    These columns are summarized as follows:

    Designation Type Depth Materials Fy(ksi)

    A - sidewall SBU 12" @base Flange: 6" x 1/4" 50
    Web: 3/16"

    B - interior pipe 10 3/4" dia. X .365" thick. 42


    E - sidewall TBU 21''@base Flange: 10''x 1/2" 50
    Web: 3/16"

    F - Endwall WF W12X14 wideflange 36

    G - Endwall SBU 12''@base Flange: 5" x 1/4" 50
    Web: 3/16"

    H - Endwall SBU 12''@base Flange: 8" x 1/4" 50
    Web: 3/16"


    All above columns to be field verified.
    TBU - Tapered Built Up column
    SBU - Straight Built Up column



    IV. Existing Column Checks & Results

    Column types noted as follows will NOT receive mezzanine loads:

    A, B & E

    Mezzanine beams and forces at these locations to be supported by the following independent
    columns:

    4"x4"x3/16" Tube columns; Fy = 46 ksi
    9" x 5" x 3/4" baseplate, K = 1.0 , pinned top and bottom
    2 - 3/4" dia. anchor bolts. Length = 11'-0 maximum

    The maximum mezzanine floor area assumed to be supported by these columns is 325 square feet.
    The following is a summary of the results of the analysis of endwall columns along line 1
    including the new mezzanine forces:

    Designation Max .Combined Stress Ratio Percent Overstressed

    Column F 1.03 3.0
    @ corner

    Column H1 0.647 ---
    8 feet from sidewall

    Column H2 0.985 ---
    34 feet from sidewall

    Column G 2.578 157.8



    The results indicate that the new mezzanine loading causes a significant overstress only
    in column type G.


    The following section will propose a reinforcement solution for the overstressed column G.


    V. Proposed Column Modification Solutions


    There are three main options which appear appropriate for the new forces and conditions:

    Option1: Build up and reinforce the column member by coverplating
    to improve its section properties including moments of inertia, rx , ry, section modulus,
    etc., along with the compression flange area to accommodate the significantly increased
    axial loads.

    Option 2: Replace the existing column with a new column.

    Option 3: Support the new mezzanine loads with independent, separate columns as is the
    case in the other area of the mezzanine.

    Option 1: Column G Coverplating

    In order to meet required combined allowable stresses the existing column will need the
    following field-installed materials:

    two --- 2 x 1/2 inch 50 ksi plates field welded to the girt side inner flange of the column.

    one --- 4 x 1/2 inch 50 ksi plates field welded to the inside flange of the column.


    Option 3: Replace the existing Column

    This option represents a significant contrast to Option 1 and is not considered in this
    investigation.

    Option 3: Add new Support Column

    This option represents a significant contrast to Option 1 and is not considered in this
    investigation.


    VI. Conclusions and notes


    Only one endwall column (G) was found to be overstressed and requiring
    reinforcement through coverplating. Assumptions and design consideration for this
    investigation is as follows:

    --- The mezzanine system is independently laterally braced. Columns investigated do not
    carry lateral mezzanine loads or forces.

    --- Columns must be properly braced at the mezzanine level by the mezzanine system.

    --- All built up columns supporting mezzanine beams must have their web-flange welds
    reinforced on the opposite side of all conrac welds 6''above and below the mezzanine
    beams.

    --- Minimum of 4 rows of two 3/4 '' diameter bolts for mezzanine framing into the 3/16"
    built up column webs for bearing.

    --- All columns materials dimensions to be field verified.



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